<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <title>App</title>
    <style>
      *{
        margin: 0;
        padding: 0;
      }
      body {
        height: 100vh !important;
        width: 100vw;
        display: flex;
        align-items: center;
        justify-content: center;
        background: lightgray;
      }
    </style>
  </head>
  <body>
      <h3 id="msgId">加载中...</h3>
  </body>
</html>
